Motor-driven compressor



Patented Feb. 24, 1953 MOTOR-DRIVEN COMPRESSOR Hans Dietler, Schwanden, Switzerland, assignor to ThermaFabrik fiir elektrische Heizung A G Schwanden, Switzerland, a Swiss company Application March 12, 1949, Serial No. 81,156 In Swi ze l n M ch. 12., 1.

1 Claim.

Thepresent. invention relates to a motor-driven compressor in which the rotor of the electric motor and the rotary compressor coupled to it are totally enclosed in a casing and the stator of the motor lies outside this casing.

All attempts to employ motor-driven compressors of this kind in refrigerators have hitherto failed because of the poor efiiciency of such sets, which is to be attributed to the difiiculty in as sembling and, in connection therewith, the necessarily too large dimensions of the air gap in the electric motor. In fact, the outwardly situated stator makes it necessary to have a cylindrical part lying in the air gap and surrounding the rotor; this cylindrical part must be gastight and sufficiently strong because of the internal pressure.

The present invention aims at providing a practically satisfactory elimination of the drawbacks, in that according to the invention the casing, made of non-magnetic material, is accurately mechanically machined to exact dimensions outwardly and inwardly at its cylindrical part lying in the air gap, after which-on a supporting ring arranged in the part intended for taking the rotary compressor-a surface standing at right angles to the axis of the motor-driven compressor is machined accuratelv fiat, and then to this surface-by adopting fitting members serving for centering-the exactly flat-machined part of a plate carrying the rotary compressor, the rotor of the motor and their common shaft is fixed, and to a flange surrounding an opening on the casing a cover is welded gastight. through which pass the suction and delivery pipes of the compressor.

This method has the special advantage that the set can be run in trial service before the covermade for instance of sheet metal-is welded to the casing. This cover, with the delivery pipe passing through it and the passage for the suction pipe inserted airtight in the bearing plate, can finally be laid on and connected airtight with the enclosed casing and the suction pipe by welding or suchlike, the risk of distortion being already reduced by the fact that casing-foot, bearing ring and plate form together a stable construction, and this risk is completely eliminated in that the casing may be provided with a flange of the diam-- eter of the cover edge and the edges can be welded together on their periphery, and a distorting of the turned-over edge is not transmitted to the casing.

In the accompanying drawing one execution of the object of the invention is diagrammatically illustrated by way of example, where:

Fig. lshows a vertical section of a motor-driven compressor on the line II in Fig. 2 and Fig. 2 a cross-section on the line EL -II in Fig. 1.

The motor-driven compressor in the drawing has the electric motor with the rotor I and the stator 2 and the rotary compressor 4 arranged with the rotor on a common shaft 3. The stator 2 with the windings 5 is fixed by means of a ring 6 which is carried by arms 'I' on a casing 8. The casing 8 encloses the rotor I and the rotary compressor 4 airtight against the outside, for which purpose a closing cover 9 is welded to the flange 8' of the casing 8.

A narrowed cylindrical part 8" of the casing lies in the air gap of the electric motor between its rotor I and stator 2. In a widened lower part 8" of the casing 8, which contains the rotary compressor 4, a bearing ring H] is fixed, for instance by firm welding, whose under surface I0 is machined exactly fiat and lies in a plane standing at right angles to the axis of the motor-driven compressor. The ring I0 serves as erecting ring for the bearing plate I I of the rotary compressor 4. The edge of the plate II projecting over the periphery of this compressor is, together with the whole plate, ground accurately flat. Between plate II and ring In dowel pins [5 are arranged and screw-bolts l2 serve to connect plate II to ring In.

Suction pipe l3 of the rotary compressor 4 is inserted airtight into plate I l whilst the delivery pipe I4 is welded into the closing cover 9 and passes with its inner end through a hole in plate The assembling of the described motor-driven compressor is effected in tin: following manner.

The cylindrical part 8" of the casing 8 is machined accurately to dimensions outwardly and inwardly, for instance by drawing, turning and grinding. After that, the supporting ring l0, which is fitted on the part 8 of the casing 8, is accurately fiat machined on the surface In on a plane standing exactly at right angles to the axis of the casing 8. The supporting plate H is now also accurately machined; then the rotor I, fixed exactly central on the plate, the shaft 3 and the rotary compressor, are securely fixed by means of this plate to the supporting ring Ill.

The exactly central position of these parts to the ring 10 is ensured by the above-mentioned dowel pins. The centering could, however, also be effected by means of annular shoulders and grooves on ring l0 and plate I I.

The cover 9 with the delivery pipe 14 welded in it is then firmly welded airtight by means of its edge to the flange part 8 of the casing 8 and likewise the suction pipe l3 passing through an opening in the cover 9 in this opening.

The casing 8 consists naturally of non-magnetic material and for instance of stainless steel. In order that the air gap in the motor may not be too large, the wall thickness of the casing, or at least of the part 8" must be as small as possible. But within the casing 8 there is overpressure while the compressor is working, and this circum stance must also be taken into consideration when choosing the wall thickness.

It is therefore well, with slight wall thickness of the casing, to keep the diameter of the part 8" of the casing 8 also slight and to give a correspondingly greater axial length to the rotor i and the stator 2 in order that the requisite motor output may nevertheless be attained. The part 8" can then be inserted as a close fit into the stator bore in order that the stator may take over a part of the pressure exerted on the casing.

What I claim is:

In a combined motor-compressor assembly; the combination of a motor stator definin a central hollow space, a stepped cylindrical sheath havin a small diameter portion fitting closely into said hollow space and an integral and coaxial large diameter portion, said sheath being axially open at the end defined "by said large diameter portion and closed at the opposite end thereof, a rotor adapted to be rotatably enclosed in said small diameter portion of the sheath, a rotary compressor operatively connected to said rotor in axial alignment with the latter and adapted to be disposed within said large diameter portion of the sheath, a mounting ring fixedly secured within said large diameter portion of the sheath and having an internal diameter sufiicient to permit said rotor and compressor to pass there through, a supporting plate for said compressor having a diameter less than that of said large diameter portion of the sheath but greater than said internal diameter of the ring t abut against the face of the latter directed toward said open end of the sheath, means for detachably securing said supporting plate to said mounting ring with said rotor and compressor centered relative to said hollow space defined by the stator, and closure means for sealing said open end of said sheath.

HANS DIETLER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,263,633 Zoelly Apr. 23, 1918 1,911,128 Apple May 23, 1933 2,153,563 I-lubacker Apr. 11, 1939 2,163,194 Davis June 20, 1939 2,174,536 Smith Oct. 3, 1939 2,283,763 Roglin 1 May 19, 1942 2,545,600 Berry Mar. 20, 1951 

